CN101545816A - Pressure Sensor - Google Patents

Abstract

The present invention provides a pressure sensor that does not use oil as an internal pressure medium, realizes miniaturization by simplifying the structure of a force transmission member, and has improved measurement accuracy and good sensitivity for pressure detection. A first diaphragm (5) that bends with the pressure of the liquid to be measured is installed on the front end of the first pressure input port (2) of the housing (4), and is installed on the front end of the second pressure input port (3). There is a second diaphragm (6) that bends with atmospheric pressure. A shaft (7) is installed between the first diaphragm (5) and the second diaphragm (6). A movable part (9) is installed at a predetermined position of the shaft (7). The pressure sensitive element (11) is fixed by respectively connecting and supporting the support parts at both ends on the movable unit (9) and the fixed unit (10), and the detection of the force along the support parts at the two ends of the pressure sensitive element (11) Axis direction is configured. The pressure sensitive element (11) is configured so that its displacement direction is the same as that of the shaft (7).

Description

Pressure Sensor

technical field

The invention relates to a pressure sensor, and is suitable for realizing the diversification of the use of the pressure sensor by not using oil as the pressure medium of the pressure sensor.

Background technique

Conventionally, pressure sensors using piezoelectric vibrating elements as pressure sensitive elements, such as water pressure gauges, barometers, and differential pressure gauges, are known. The piezoelectric vibrating element is formed, for example, by forming an electrode pattern on a plate-shaped piezoelectric substrate, setting a force detection direction as a detection axis, and when a pressure acts in the direction of the detection axis, the piezoelectric vibrating element The resonance frequency of the sensor changes, and the pressure is detected according to the change of the resonance frequency. Patent Documents 1 to 3 disclose pressure sensors using piezoelectric vibrating elements as pressure sensitive elements. When pressure is applied to the bellows through the pressure inlet, the force corresponding to the effective area of the bellows will be transferred in the form of compressive force or tensile force through the force transmission unit with the pivot (flexible hinge) as the fulcrum. A force F is applied to the piezoelectric vibrating element. A stress corresponding to the force F is generated in the piezoelectric vibrator, and the resonance frequency is changed by the stress. This pressure sensor measures pressure by detecting a change in resonance frequency generated by piezoelectric electrons.

A conventional pressure sensor will be described using an example disclosed in Patent Document 1 and the like. FIG. 11 is a schematic diagram showing the structure of a conventional pressure sensor.

The existing pressure sensor 101 shown in Fig. 11 includes: a frame body 104 having a first pressure input port 102 and a second pressure input port 103 disposed oppositely; and a force transmission unit 105 inside the frame body 104, and The first bellows 106 and the second bellows 107 are connected by one end of the force transmission unit 105 . In addition, the other end of the first bellows 106 is connected to the first pressure input port 102 , and the other end of the second bellows 107 is connected to the second pressure input port 103 . Furthermore, a double tuning fork vibrator 109 is disposed as a pressure sensitive element between the other end of the force transmission unit 105 and the end of the substrate 108 on the non-fulcrum (fulcrum) side.

Here, in the pressure sensor, when detecting pressure with high precision, the inside of the bellows is filled with liquid. The liquid generally uses oil such as silicone oil with high viscosity to prevent air bubbles from entering or accumulating inside the bellows or inside the corrugated part.

In this way, the viscous oil 110 is filled inside the first bellows 106, and when the object of pressure measurement is liquid, the liquid and the oil 110 come into contact and face each other through the opening 111 opened in the first pressure input port. In addition, the opening diameter of the opening 111 is set so that the oil 110 does not leak to the outside.

In the pressure sensor 101 thus constituted, when the pressure F is applied to the oil 110 filled inside the first bellows 106 by the liquid to be measured, the pressure F is applied to the force transmission unit 105 via the first bellows 106 (by One end of the swing rod supported by the fulcrum). On the other hand, atmospheric pressure is applied to the second bellows 107 , and a force corresponding to the atmospheric pressure is also applied to one end of the force transmission unit 105 .

As a result, there is a pressure difference between the pressure F applied by the liquid to be measured and the atmospheric pressure, and a force corresponding to the pressure difference takes the fulcrum of the substrate 108 as a fulcrum, passes through the other end of the force transmission unit 105, It is applied to the double tuning fork type vibrating member 109 as a compressive force or a tensile force. When a compressive force or tensile force is applied to the double tuning fork vibrator 109, stress is generated in the double tuning fork vibrator 109, and the resonance frequency changes according to the magnitude of the stress. Therefore, the pressure can be detected by measuring the resonance frequency. F size.

On the other hand, in Patent Document 4, a pressure sensor with a structure using a swing lever with a fulcrum (flexible hinge) as a fulcrum used in the above-mentioned pressure sensor is proposed without using a high-cost force transmission unit ( cantilever). In the sensor case, two bellows are arranged in a straight line, and a support is sandwiched between the bellows, and the pressure fluctuation caused by the difference in pressure introduced into each bellows is detected by the movement of the support. . Thus, the support for vibrator bonding is sandwiched between one end of the first bellows and one end of the second bellows, and both ends of the pressure sensitive element are respectively fixed to the outer peripheral side of the second bellows. The support and the shell wall on the other end side of the second bellows. Furthermore, the following structure is adopted: the reinforcing plate is arranged and the pressure-sensitive element sandwiches the second bellows at a line-symmetrical position, and the two ends of the reinforcing plate are respectively fixed on the support and the wall surface of the housing.

Furthermore, in Patent Document 5, in order to solve the problem that the strength of the pressure sensor disclosed in Patent Document 4 is weak against an impact from a direction perpendicular to the direction of the pressure detection axis of the bellows, it is proposed as follows The pressure sensor: in the direction perpendicular to the direction of the pressure detection axis, the supporting elastic unit (so-called spring) is used to connect the support and the shell.

Next, Patent Documents 6 and 7 disclose pressure sensors that are fixed to an engine block and used to detect oil pressure inside the engine. This pressure sensor is composed of the following units: a sensor part that outputs an electrical signal corresponding to the applied pressure; a pressure-receiving diaphragm part that receives pressure; and a pressure transmitter for transmitting pressure from the diaphragm part to the sensor part Unit, specifically, a first diaphragm for pressure bearing is provided on one end of the hollow metal cylinder, a second diaphragm for detection is provided on the other end, and a gap between the first diaphragm and the second diaphragm in the cylinder A force transmission unit is interposed between them. The force transmission unit is a shaft made of metal or ceramics, which is sandwiched between a pair of diaphragms in a prestressed state. Moreover, a chip as a pressure detection element and having a strain gauge function is attached to the outer end surface of the second diaphragm, and the pressure received by the first diaphragm is transmitted to the second diaphragm through the force transmission unit, and passed through the strain gauge chip. The deformation of the second diaphragm is converted into an electrical signal to detect the engine oil pressure.

[Patent Document 1] Japanese Patent Laid-Open No. 56-119519

[Patent Document 2] Japanese Patent Application Laid-Open No. 64-9331

[Patent Document 3] Japanese Patent Application Laid-Open No. 2-228534

[Patent Document 4] Japanese Patent Laid-Open No. 2005-121628

[Patent Document 5] Japanese Patent Laid-Open No. 2007-57395

[Patent Document 6] Japanese Patent Laid-Open No. 2006-194736

[Patent Document 7] Japanese Patent Laid-Open No. 2007-132697

However, in the inventions of Patent Documents 1 to 3, as in the pressure sensor shown in FIG. The thermal expansion coefficient of the oil 110 is larger than that of the tuning fork vibrator 109, etc., so that the components constituting the pressure sensor are thermally deformed due to temperature changes. Such thermal deformation acts on the double-tuning-fork vibrator 109 as unnecessary stress, and therefore there is a problem that errors occur in measured pressure values, deteriorating the characteristics of the pressure sensor.

In addition, although the oil 110 filled in the first bellows 106 is in contact with and faces the liquid to be measured for pressure, depending on how the pressure sensor is installed, the oil 110 may flow out to the liquid to be measured for pressure, or the liquid may Since it flows into the first bellows 106 side, air bubbles may be generated in the oil 110 filled in the first bellows 106 . When air bubbles are generated in the oil 110 , the oil 110 functioning as a pressure transmission medium cannot stably transmit force to the double tuning fork vibrator via the force transmission unit 105 , and thus pressure measurement errors may occur.

Furthermore, as described above, since the oil 110 is in contact with and faces the liquid to be measured for pressure, depending on the installation method of the pressure sensor, the oil 110 may flow out to the side of the liquid to be measured for pressure, so that foreign substances may be mixed in the pressure sensor. When measuring the pressure of a clean liquid, there is a problem that the conventional pressure sensor using the oil 110 cannot be used.

Furthermore, in addition, the force transmission unit 105 of the conventional pressure sensor 101 has a complicated structure, which prevents the miniaturization of the pressure sensor. In addition, since the force transmission unit 105 needs to be configured as a flexure hinge with a thin diameter portion, it becomes an expensive component, which raises the problem of increasing the manufacturing cost of the pressure sensor.

In the pressure sensors proposed in Patent Documents 4 and 5, when the bellows sags when tilted, there is a problem that the force applied to the pressure sensitive element (double tuning fork vibrator) changes, and the resonance frequency also changes.

Furthermore, since a pipe (pipe) filled with oil is connected to the pressure inlet of the pressure sensor, and the other end of the pipe is brought into contact with the liquid to be measured, as disclosed in Patent Documents 1 to 3, In this way, the oil filled in the bellows or the tube is in contact with the liquid to be measured, so depending on the installation method of the pressure sensor, the oil may flow out to the side of the liquid to be measured, or the liquid may flow into the bellows. Therefore, air bubbles may be generated in the oil filled in the bellows. If air bubbles are generated in the oil, the oil that functions as a pressure transmission medium cannot transmit the force stably to the double tuning fork through the support. Type vibrating parts, so there is a problem of pressure measurement errors.

In Patent Document 5, since the pressure sensor is configured such that the holder sandwiched between the bellows is supported on the side of the housing via a reinforcing elastic member made of a leaf spring, it is undeniable that such a force acts: , this force inhibits the action of the bearing as the bellows moves axially. As a result, pressure detection sensitivity may decrease. In addition, if the hardness of the reinforcing elastic member is increased in order to reinforce the support, the movement of the bellows will be suppressed, thereby deteriorating the pressure detection sensitivity.

Furthermore, in Patent Documents 4 and 5, since the reinforcement plate and the pressure sensitive element are disposed at line-symmetrical positions facing each other with the bellows interposed therebetween, there is a problem that the motion of the bellows is suppressed, thereby reducing the pressure detection sensitivity.

In Patent Documents 6 and 7, although the diaphragm and the shaft are in contact with a prestressed state, since the pressure sensor is used under high-temperature and high-pressure conditions, if it is fixed rigidly, it may be caused by the thermal expansion of each part. Therefore, in consideration of the thermal expansion, the diaphragm and the shaft are only brought into point contact, and no adhesive or other bonding methods are used for adhesion. Therefore, when the diaphragm and the shaft move due to pressure fluctuations, there is a high possibility that the point contact parts will deviate from each other. During the deviation of the contact point, the force acting on both the diaphragm and the shaft will leak, so there is a problem that it cannot be performed. The problem of high-precision pressure detection. In addition, since the pressure sensors described in Patent Documents 6 and 7 are originally used under high temperature and high pressure conditions, in order to leave a distance between the pressure receiving part and the sensing part to avoid thermal influence on the chip of the sensing part, etc. , it is preferable that the force transmission unit be as long as possible, and therefore, it is not preferable to be applied to a technique for miniaturization. In addition, in the case of Patent Documents 6 and 7, a shaft is interposed between a pair of diaphragms to transmit force. However, since the sensor chip is mounted on the diaphragm of the sensor part, the properties of the diaphragm The difference between the pressure receiving side and the sensor part side has a big disadvantage that the measurement accuracy cannot be improved.

Contents of the invention

Therefore, the present invention has been accomplished in view of the above-mentioned various problems, that is, its object is to provide a pressure sensor that does not use oil as an internal pressure medium and realizes the pressure sensor by simplifying the structure of the force transmission unit. Miniaturization is realized, and the measurement accuracy of pressure detection is improved, and the sensitivity is good.

The invention has been made to solve at least a part of the problems described above, and the invention can be implemented by the following forms or application examples.

[Application example 1] A pressure sensor, characterized in that the pressure sensor includes: a housing; a diaphragm that closes the pressure input port of the housing, and one side of the diaphragm is a pressure-bearing surface; and a pressure sensitive part, which Taking the detection direction of the force as the detection axis, one end of the pressure sensitive part is connected to the central area of the other side of the diaphragm, and the other end of the pressure sensitive part is connected to the housing, and the detection axis is approximately perpendicular to the pressure-bearing surface.

According to such the present invention, the diaphragm is used as the pressurized medium that bears the pressure in the pressure-measuring environment, and oil as the pressure-bearing medium is not needed in the pressure sensor. Therefore, no oil will flow out into the pressure-measuring environment. It can be used, for example, for applications such as pressure measurement of a clean liquid in which foreign matter is not allowed to be mixed as an environment to be pressure measured.

In addition, since oil with a large thermal expansion coefficient is avoided as a pressure medium, the temperature characteristics of the pressure sensor can be greatly improved.

[Application example 2] The above-mentioned pressure sensor is characterized in that the pressure-sensitive part is composed of the following units: a force transmission unit, one end of which is in contact with the central area of the other surface of the diaphragm; a movable unit, which is fixed on the force transmission unit; and a pressure sensitive element, one end of which is connected with the movable unit, and the other end is connected with the shell.

According to the present invention as described above, the pressure sensor can be reduced in size and reduced in cost because it does not require a costly and complicated force transmission unit and thus can be simplified.

[Application example 3] The pressure sensor as described above, wherein the force transmission unit is a shaft.

According to such the present invention, unnecessary deformation of the pressure sensitive element can be avoided.

[Application example 4] The pressure sensor as described above, wherein the pressure sensitive element has bases provided at both ends of the pressure sensitive element, and there is vibration between the bases provided at the two ends. department.

According to the present invention, a pressure sensor can be easily realized by using a double-tuning fork vibrator, a thickness-shear vibrator, or a surface acoustic wave device whose resonance frequency changes due to tensile or compressive stress generated by the pressure sensitive element. In particular, since the double-tuning-fork vibrating element has good sensitivity to tensile and compressive stresses and has excellent resolution capability, the use of the double-tuning-fork vibrating element can realize a pressure sensor for detecting a small pressure difference.

[Application Example 5] The above-mentioned pressure sensor is characterized in that the material of the diaphragm is metal, ceramic or piezoelectric crystal.

According to such the present invention, as for the material of the diaphragm, a material with excellent corrosion resistance such as metal or ceramics such as stainless steel or a single crystal such as crystal is selected and used according to the material of the measurement object, so that a high measurement accuracy can be configured. And stable pressure sensor.

[Application Example 6] The above-mentioned pressure sensor is characterized in that the material of the shaft is stainless steel, aluminum or ceramics.

According to such the present invention, as for the material of the shaft, a high-strength and stable material such as stainless steel or aluminum, or ceramics, which are easy to process, can be selected and used according to the application of the pressure sensor, thereby making it possible to configure a high-precision and stable pressure sensor. sensor.

[Application example 7] The above-mentioned pressure sensor is characterized in that the material of the housing is stainless steel, aluminum or ceramics.

According to such the present invention, the influence of heat on the deformation of the pressure sensitive element can be alleviated.

[Application example 8] A pressure sensor, characterized in that the pressure sensor includes: a housing with a pressure input port; a diaphragm that closes the pressure input port of the housing, and the outer surface of the diaphragm is a bearing a pressure surface; and a pressure-sensitive part, inside the housing, one end of the pressure-sensitive part is connected to the central area of the inner surface of the diaphragm, the other end is connected to the housing, and the pressure-sensitive part is connected to the membrane along the The axis perpendicular to the pressure-bearing surface of the sheet sets the detection axis.

According to such the present invention, the diaphragm is used as the pressure medium to withstand the pressure in the environment to be pressure measured, and oil as the pressure medium is not required in the pressure sensor. In applications such as pressure measurement, and because oil with a large thermal expansion coefficient is avoided as a pressure medium, the temperature characteristics of the pressure sensor can be greatly improved. In addition, since the pressure-sensitive part is accommodated in the case, it is possible to achieve miniaturization.

[Application example 9] On the basis of the pressure sensor in the application example 1, it is characterized in that the pressure sensitive part is composed of a force transmission unit connected vertically to the diaphragm, and one end is connected to the force transmission unit and the other end is It is composed of a pressure sensitive element connected with the wall surface of the housing.

According to the present invention as described above, since the force transmission unit having the support shaft structure is not required and simplification is achieved, it is possible to reduce the size and cost of the pressure sensor.

[Application Example 10] A pressure sensor, characterized in that the pressure sensor includes: a housing; a pressure input port coaxially arranged on the opposite wall surface of the housing; a diaphragm closing the pressure input port , and the outer surface of the diaphragm is a pressure-bearing surface; a force transmission unit, which is connected to the central area of the inner surface of the diaphragm inside the housing; and a pressure sensitive element, one end of which is connected to the force transmission unit, The other end is connected to the housing, and the pressure sensitive element sets a detection axis along an axis perpendicular to the pressure bearing surface of the diaphragm.

According to such a configuration, an oil-free and compact pressure sensor can be used as an absolute pressure sensor.

[Application example 11] A pressure sensor, characterized in that the pressure sensor includes: a housing; a pair of pressure input ports, which are arranged on the opposite walls of the housing; first and second diaphragms, which close the The pressure input port, and the outer surfaces of the first and second diaphragms are pressure-bearing surfaces; the force transmission unit is in the central area between the interior of the housing and the inner surfaces of the first and second diaphragms connection; and a pressure sensitive element, one end of which is connected to the midway of the force transmission unit, and the other end is connected to the housing, and the pressure sensitive element sets the detection axis parallel to the axis perpendicular to the pressure bearing surface of the diaphragm .

According to this configuration, an oil-free and compact pressure sensor can be used as a relative pressure sensor.

[Application example 12] The pressure sensor according to any one of application examples 8 to 11, wherein a guide shaft parallel to the detection axis is provided inside the housing.

According to this structure, since only the force along the direction of the detection axis can act on the pressure sensitive element, detection accuracy can be improved.

[Application example 13] In the pressure sensor according to any one of application examples 10 to 11, the force transmission unit is formed of a shaft, and a pressure sensitive element is arranged parallel to the shaft.

According to this configuration, it is possible to reduce the height of the housing and promote miniaturization.

[Application example 14] In the pressure sensor according to any one of application examples 10 to 11, the force transmission unit is formed of a shaft, and a pressure sensitive element is arranged coaxially with the shaft.

According to this structure, the pressure sensor for absolute pressure detection can be comprised with a simple structure, and cost can be reduced.

[Application example 15] A pressure sensor, characterized in that the pressure sensor includes: a housing, which is composed of opposite end plate-shaped first and second housings and surrounding these housings and forming side parts The third shell is formed; the flange is arranged on one of the shells; the first and second diaphragms close the pressure input openings of the first and second shells; the central shaft , in the housing, the central axis connects the first and second diaphragms in the central area of the first and second diaphragms to form a whole, so that force transmission can be carried out; pressure sensitive element, the two ends of which are installed on the movable support fixed on the central axis and the fixed support provided on the inner surface of the housing, and the detection axis of the pressure sensitive element is set to be aligned with the center the axes are parallel; and a plurality of supporting rods are arranged around the central axis and connect the first and second shells.

According to such application example 15, in addition to the transmission of pressure without using oil, in particular, high-precision pressure measurement can be performed by a plurality of support rods regardless of the mounting posture of the housing. The housing with the rim serves as a mounting base when mounting to the liquid container to be measured, so that unnecessary stress will not be applied to pressure-sensitive parts such as the center shaft during mounting.

[Application example 16] A pressure sensor, characterized in that the pressure sensor includes: a housing, which consists of mutually opposed end plate-shaped first and second shells and surrounding these shells and forming side parts The third casing is formed; the first diaphragm closes the pressure input port opening in the first casing; the central axis is in the housing, and the central axis is in the central area of the first diaphragm It is integrated with the first diaphragm so as to be able to transmit force; the two ends of the pressure sensitive element are installed on the movable support fixed on the end of the central axis and arranged on the said On the fixed support of the inner surface portion of the second housing, and the detection axis of the pressure sensitive element is set to be coaxial with the central axis; and a plurality of support rods, which are arranged around the central axis, And connect the first and second shells.

With such a configuration, it is possible to form a pressure sensor that does not use oil, and it is possible to form a pressure sensor for absolute pressure detection with a simple structure and reduce costs.

[Application example 17] The pressure sensor according to application example 16 or 17, wherein the central shaft and the movable support are integrally formed of one material by cutting.

Thereby, it is possible to prevent the fixed part as the central axis from rattling and shifting relative to the support.

[Application example 18] The pressure sensor according to application example 16 or 17, wherein the connecting portion of the central shaft and the connecting portion of the diaphragm are integrally bonded by an adhesive.

In this configuration, it is possible to prevent the diaphragm from being displaced from the central axis, and to prevent a decrease in measurement accuracy.

Description of drawings

FIG. 1 is a schematic diagram showing the structure of a first embodiment of a pressure sensor according to the present invention.

FIG. 2 is a schematic diagram showing the structure of the housing 4 of the pressure sensor 1 .

Fig. 3 is a flow chart showing the assembly procedure of the pressure sensor according to the present invention.

Fig. 4 is a diagram illustrating an assembly method using a positioning jig.

Fig. 5 is a schematic diagram showing the structure of a second embodiment of the pressure sensor according to the present invention.

Fig. 6 is a schematic sectional view of a pressure sensor according to a third embodiment.

Fig. 7 is a perspective view of main parts of the pressure sensor.

Fig. 8 is a partially cutaway perspective view of the pressure sensor.

FIG. 9 is an assembly process diagram of the pressure sensor.

Fig. 10 is a schematic sectional view of a pressure sensor according to a fourth embodiment.

FIG. 11 is a cross-sectional view showing a structural example of a conventional pressure sensor.

Label description

1, 30: pressure sensor; 2: first pressure input port; 3: second pressure input port; 4, 36: housing; 5: first diaphragm; 6: second diaphragm; 7, 32: shaft; 9 : movable part; 10, 35: fixed part; 11: pressure sensitive element; 12a, 12b: support rod; 20, 31: first shell; 21, 33: second shell; 22: third shell; 25 : positioning fixture; 26: orifice; 27: first component; 28: second component; 40: pressure sensor: 42: shell; 44: flange end plate (first shell); 46: sealed terminal block; 47 : first pressure input port; 48: cylinder side wall; 49: second pressure input port; 50: first diaphragm; 52: second diaphragm; 54: central shaft; 56: movable part; 58: pressure sensitive Component; 60: boss portion; 62a, 62b: support rod (guide shaft); 64: sealed terminal; 70: pressure sensor; 72: housing; 74: flange end plate (first housing); 76: sealed terminal platform; 77: pressure input port; 78: cylinder side wall; 80: diaphragm for pressure bearing; 84: central shaft; 86: movable part; 88: pressure sensitive element; 90: support; 92a, 92b: support rod (guiding axis).

Detailed ways

Hereinafter, the present invention will be described in detail based on the illustrated embodiments. In addition, each embodiment will be described by taking the case where the object to be measured is a liquid as an example.

FIG. 1 is a schematic diagram showing the structure of a first embodiment of a pressure sensor according to the present invention.

The pressure sensor 1 shown in FIG. 1 includes a case 4 for accommodating various components described later. The inside of the case 4 is vacuum, and has a first pressure input port 2 and a second pressure input port 3 disposed opposite to each other. A first diaphragm (diaphragm for pressure receiving) 5 that bends according to the pressure of the liquid to be measured is attached to the front end of the first pressure input port 2, and the first diaphragm 5 is exposed to the outside. A second diaphragm (diaphragm for atmospheric pressure) 6 that bends according to atmospheric pressure is attached to the front end portion of the second pressure input port 3 . A shaft 7 serving as a force transmission unit is installed between the first diaphragm 5 and the second diaphragm 6 and is exposed to the outside. A movable part 9 is installed at a predetermined position of the shaft 7 . The pressure sensitive element 11 is fixed by connecting and supporting the support portions at both ends on the movable part 9 and the fixed portion 10 of the second housing 21 respectively, and the two ends of the pressure sensitive element 11 are arranged along the direction of the force detection axis. The displacement direction of the pressure sensitive element 11 is configured to be the same as the displacement direction of the shaft 7 of the pressure receiving part connecting the first diaphragm 5 and the second diaphragm 6 , that is, parallel to the direction of the force detection axis. Support rods 12a, 12b are provided between the first housing 20 and the second housing 21, and the inner surfaces of the first housing 20 and the second housing 21 are formed with cross sections shaped like the support rods 12a, 12b. The shape of the dowel hole (not shown), the support rods 12a, 12b as the guide shaft are inserted into the dowel hole to engage with it, so as to avoid the pressure sensitive element from being damaged when assembling and using the product. The necessary deformation functions. In addition, although two support rods are formed in the figure, it is also possible to form one or more than three.

Referring to FIG. 1 and FIG. 2 , the first embodiment will be described in more detail. The pressure sensor 1 has a housing 4 made of a hollow cylinder. The casing 4 is composed of three components: a first shell (lower end plate) 20 as an end plate, a second shell (upper end plate) 21, and a third shell 22 as a cylindrical side wall, and the inside of the shell 4 is hollow. On the outer end surfaces of the first housing 20 and the second housing 21, protrudingly provided with joints as the first mounting part and joints of the second mounting part along the axis of the housing 4, external threads are cut out on these joints. , to form the mounting fitting 13 as a connecting portion for introducing the liquid to be measured or the atmosphere. In the first and second shells 20, 21 (including the joint part), the first pressure input port 2 and the second pressure input port 3 communicated with the inner space are concentrically penetrated with the shell shaft core, and at the joint part opening at the front end. In addition, diaphragms are installed on the outer end surfaces of the joints to respectively close these pressure input ports 2 and 3 and separate the inside and outside. In this embodiment, the first diaphragm 5 for receiving pressure is attached to the first case 20 side, and the second diaphragm 6 for setting atmospheric pressure is attached to the second case 21 side. These diaphragms 5, 6 are identical, and both are set so as to have the same amount of deflection when subjected to the same pressure. Of course, by doing so, the casing 4 is in a state where the inside and the outside are blocked, and the inside can be kept in a vacuum state by an air extraction device (not shown).

In such a shell structure, there is a pressure-sensitive part with the force detection direction as the detection axis inside the shell 4, one end of the pressure-sensitive part is connected to the central area of the other side of the diaphragm, and the pressure-sensitive part The other end of the sensitive part is connected to the housing, and the detection axis is approximately perpendicular to the pressure bearing surface. That is, the central shaft 7 constituting a part of the pressure sensitive part is arranged along the axial center of the housing 4, and penetrates the first pressure input port 2 and the second pressure input port 3, and the front end of the central shaft 7 is passed through the adhesive. It is fixedly connected to the central area of the above-mentioned diaphragms 5,6. Thereby, bending deformation of one of the diaphragms 5 and 6 can be transmitted to the other. That is, the center shaft 7 constitutes a force transmission member. The central shaft 7 is made of metal such as stainless steel or aluminum, or ceramics, and is formed of a rigid material that does not undergo deformation such as buckling. When reducing the weight of this central shaft 7, it can be formed with a pipe. In the middle of the central shaft 7, a small assembly as a mounting support for the pressure-sensitive element described later is provided through integral molding or added later, and the small assembly serves as a movable part 9 that moves along with the axial movement of the central shaft 7. The central shaft 7 and the movable part 9 may also be integrally formed from one member by cutting. In this way, the movable part 9 does not shake or deviate on the fixed part of the central shaft 7, so the detection accuracy is improved.

In addition, a pressure-sensitive element 11 constituting the main body of the pressure-sensitive part is cooperatively connected to the central shaft 7 . In the embodiment, the pressure-sensitive element 11 adopts a double-tuning-fork vibrator, and the installation support part on one end side is fixed to the movable part 9 , and the installation support part on the other end side is fixed to the fixed part 10 of the second housing 21 mentioned above. At this time, the pressure sensitive element 11 is arranged in such a manner that the detection axis is set parallel to the central axis 7 and force transmission is performed so that the center is perpendicular to the pressure receiving surface of the first pressure receiving diaphragm 5 . Axial changes on the shaft become changes along the detection axis of the pressure sensitive element 11 via the movable part 9 . In addition, a recessed portion is formed on the second case 21 so as to form a side surface aligned with the side surface of the movable portion 9, and the pressure sensitive element 11 is mounted parallel to the central axis 7, thereby reducing the height of the case.

A plurality of support rods 12 a , 12 b serving as guide shafts are disposed inside the housing 4 in parallel with the central axis 7 and located around it. The support rods 12a, 12b keep the distance between the first housing 20 and the second housing 21 fixed, so as to avoid the deformation of the housing 4 caused by external force or any posture, which will cause the detection accuracy to decrease. To this end, the ends of the support rods 12 are pressed into dowel holes formed in the first housing 20 and the second housing 21 to be stably fixed.

As shown in FIG. 1 , the pressure sensor 1 constructed in this way is installed on a storage container for the liquid to be measured by cutting out the mounting fittings 13, 13, etc., which have helical grooves around them to function as threads, so that the first membrane The sheet 5 is in direct contact with the liquid to be measured. The attachment fittings 13 and 13 need to have a predetermined shape and wall thickness according to the pressure strength of the liquid to be measured and the structure of the liquid storage container.

The first diaphragm 5 is an elastic pressure-bearing element. When pressure is applied from the contacted liquid side, the first diaphragm 5 bends toward the central axis 7, and the movable unit 9 moves along the paper in FIG. 1 via the central axis 7. A force F1 is applied in the up and down direction of the surface. On the other hand, atmospheric pressure is applied to the second diaphragm 6 , and the force F2 is applied to the movable unit 9 via the central axis 7 by the second diaphragm 6 bearing the atmospheric pressure.

In this case, on the surface of one side of the movable unit 9 (the surface parallel to the pressure-bearing surface of the diaphragm), the force F1 that is equivalent to the liquid applied to the first diaphragm 5 and the atmospheric pressure applied to the second diaphragm are applied. The force (F1-F2) of the pressure difference of the force F2 on the sheet 6, so the surface on the other side of the movable unit 9 (the surface perpendicular (crossing) to the pressure-bearing surface of the diaphragm) and the surface of the second housing 21 A compressive force or a tensile force is applied to the pressure sensitive element 11 arranged between the fixed parts 10 . When a compressive force or tensile force is applied to the pressure sensitive element 11, elongation (tension) stress or compressive stress is generated in the pressure sensitive element 11, so its resonant frequency varies with the magnitude of the stress. By measuring its resonance The frequency can be obtained by using a microcomputer or the like to obtain a relative pressure value based on the atmospheric pressure as zero.

However, when assembling the pressure sensor 1, it is necessary to avoid deformation of the pressure sensitive element 11 due to unnecessary stress. Therefore, in this embodiment, two supporting rods 12a, 12b are used to assemble the diaphragm, the shaft or the movable parts with high precision.

Next, a method of assembling the pressure sensor 1 will be described.

FIG. 2 is a schematic diagram showing the structure of the housing 4 of the pressure sensor 1 .

The case 4 is composed of the following three components: a first case 20 having a first diaphragm 5 as a pressure medium for the measurement object liquid; and a second diaphragm 6 as a pressure medium for the atmospheric pressure. the second housing 21; and the third housing 22 for hermetically sealing the pressure sensor 1. Moreover, assembly accuracy is improved by combining the first housing 20, the second housing 21 and the support rods 12a, 12b for assembly.

Next, the procedure for assembling the pressure sensor 1 will be described.

Fig. 3 is a flow chart showing the assembly procedure of the pressure sensor of the present invention.

In this case, first, the first diaphragm 5 is connected to the front end portion of the first pressure input port 2 provided in the first housing 20 ( ST1 ). Next, the second diaphragm 6 is connected to the front end portion of the second pressure input port 3 provided on the second housing 21 (ST2). Then, one end of the shaft 7 is vertically connected to the first diaphragm 5 with high precision using an assembly jig described later ( ST3 ). Furthermore, the other end of the shaft 7 is connected to the second diaphragm 6 in the vertical direction with high precision using an assembly jig described later ( ST4 ). Next, the support rods 12a, 12b are connected to the first housing 20 by inserting one end of the support rods 12a, 12b into the dowel hole of the first housing 20 connected with one end of the shaft 7 and the first diaphragm 5. connected (ST5), and then, by inserting the other end of the support rod 12a, 12b into the dowel hole of the second housing 21 connected with the other end of the shaft 7 and the second diaphragm 6, the support rod 12a , 12b are connected to the second housing 21 (ST6). Next, the movable part 9 is connected at the predetermined position of the shaft 7 (ST7), the pressure sensitive element 11 is connected between the movable part 9 and the fixed part 10, and the displacement direction of the pressure sensitive element 11 is aligned with the first diaphragm 5 and the second diaphragm 5. The displacement directions of the two diaphragms 6 are the same (ST8). Finally, the first casing 20 and the second casing 21 with the various structural elements are attached to the third casing 22 for sealing the inside of the casing (ST9), and the pressure is completed by sealing the inside of the casing in a vacuum. Assembly of the sensor 1 (ST10).

In addition, in order to improve the measurement accuracy of the pressure sensor, the shafts 7 connected to the first diaphragm 5 and the second diaphragm 6 in the vertical direction are required to ensure the verticality with high precision when connecting. Therefore, in this embodiment, the shaft is assembled by the positioning assembly method shown in FIG. 4 .

Fig. 4 is a diagram illustrating an assembly method using a positioning jig.

The positioning jig 25 is formed in a cylindrical slotted shape and can be divided into two semicircular components. And, the positioning jig 25 can be tightly inserted into the orifice 26 communicating with the first pressure input port 2 provided on the casing 4, and after the positioning jig 25 is arranged in the orifice 26, the shaft 7 is inserted into the positioning jig 25 the central part. Then, after the inserted shaft 7 is connected with the first diaphragm 5 (not shown), the first component 27 and the second component 28 of the positioning fixture 25 are separated and removed, and the shaft 7 is precisely aligned vertically. Direction is connected to the first diaphragm 5, so the measurement accuracy of the pressure sensor can be improved. In addition, the connection between the second diaphragm 6 and the shaft 7 also requires the use of the positioning fixture 25 .

The pressure sensitive element 11 used in the pressure sensor of this embodiment is made of piezoelectric materials such as crystal, lithium niobate, and lithium tantalate, and is formed as a double-tuning-fork vibrating element, a SAW resonating element, a thickness-shearing vibrating element, and the like. Both ends of the pressure sensitive element 11 are respectively connected to and supported by the movable unit 9 and the fixed portion of the fixed member 10 . At this time, the force detection direction of the pressure sensitive element 11 is set as a detection axis, and the direction connecting the two ends of the pressure sensitive element 11 is parallel to the detection axis. In addition, the pressure sensitive element 11 is electrically connected to an oscillation circuit (not shown) mounted on the case 4, and vibrates at a natural resonance frequency by an AC voltage from the oscillation circuit (not shown). In addition, when the pressure sensitive element 11 receives an elongation (tension) force or a compression force from the movable unit 9, an elongation (tension) stress or a compression stress is generated inside, so that the resonance frequency changes. In particular, compared with thickness-shear vibrators, the resonant frequency of the double-tuning fork vibrator changes greatly with respect to elongation and compression stress, and the variation range of the resonant frequency is also large, so it is suitable for detecting minute pressure A high precision pressure sensor with excellent resolution. When the double tuning fork vibrating element is subjected to elongation stress, the amplitude of the amplitude arm (vibration part) decreases, so the resonance frequency increases. Small. In addition, it is preferable to use a crystal having excellent temperature characteristics as the piezoelectric substrate of the double tuning fork type vibrator.

In addition, the material of the first diaphragm 5 and the second diaphragm 6 can be, for example, a metal such as stainless steel or a material with excellent corrosion resistance such as ceramics, which can also be a single crystal such as crystal, or other amorphous. Furthermore, it is preferable that the first diaphragm 5 which is in contact with the liquid to be measured is selected from a material that is not affected by corrosion, deterioration, etc. when in contact with the liquid. In addition, the shaft 7, the first diaphragm 5, the second diaphragm 6, and the housing 4 are preferably made of the same material, such as stainless steel, aluminum or ceramics, but different materials may also be used.

In addition, the inside of the housing of the pressure sensor is a vacuum chamber, which can improve the Q value (quality factor) of the pressure sensitive element to ensure a stable resonance frequency, thus ensuring the long-term stability of the pressure sensor.

In addition, since the same diaphragm system is used for both the pressure medium for the liquid to be measured and the pressure medium for atmospheric pressure, it is possible to improve the static pressure characteristic which is a constant pressure that does not change.

In addition, the material of the housing 4 and the shaft 7 is selected and a material with a small temperature expansion coefficient is used, so that the temperature characteristics of the pressure sensor can be improved. Especially if the shaft 7 is made of ceramics, the temperature characteristic of the pressure sensor basically depends on the temperature characteristic of the pressure sensitive element due to its small temperature expansion coefficient.

As described above, the pressure sensor according to the first embodiment does not require oil because the diaphragm is used as the medium in contact with the liquid to be measured, so oil does not flow out to the liquid side, and it can be used to detect foreign matter. The mixed clean liquid is used for pressure measurement and other purposes. In addition, in the pressure sensor described in the first embodiment, the received pressure is converted into a force by the diaphragm and transmitted to the pressure sensitive element through the shaft, so a force transmission unit with a high cost and a complicated structure like a cantilever is no longer used, so The pressure sensor can be miniaturized and reduced in cost.

Next, a second embodiment of the pressure sensor according to the present invention will be described.

Fig. 5 is a schematic diagram showing the structure of a second embodiment of the pressure sensor according to the present invention. In addition, the same code|symbol is attached|subjected to the same part as FIG. 1, and repeated description is abbreviate|omitted.

The pressure sensor of the first embodiment has the function of measuring the relative pressure displayed with the atmospheric pressure as zero reference, so the movable part 9 is connected to the pressure medium bearing the atmospheric pressure, however, the pressure sensor of the second embodiment has the function of measuring The function of measuring the absolute pressure with the vacuum state as the zero reference is characterized in that the pressure medium corresponding to the atmospheric pressure is removed, and the movable part 9 is connected only to the pressure medium corresponding to the liquid to be measured.

In the pressure sensor 30 shown in FIG. 5 , since the movable member 9 is connected only to the pressure medium corresponding to the liquid to be measured, the force generated by the liquid pressure F acts on the movable member 9 . Thus, the movable part 9 applies a force corresponding to the pressure applied to the first diaphragm 5 to the pressure sensitive element 11 as a compressive force or a tensile force. The pressure sensitive element 11 generates elongation (tensile) stress or compressive stress inside according to the applied compressive force or tensile force, thereby changing the resonant frequency. Therefore, by measuring the resonant frequency, it can be obtained using a computing device such as a microcomputer. The vacuum state is the absolute pressure value of the zero reference. Thus, in the second embodiment, the pressure sensor functions as an absolute pressure sensor.

In addition, the second embodiment is also assembled in accordance with the assembly procedure described in the first embodiment. Specifically, the product is completed through the following processes: the process of connecting the first diaphragm 5 with the first housing 31; the process of connecting the first diaphragm 5 with the shaft 32; connecting the first housing 31 with the support rod 12a, 12b; the process of connecting the shaft 32 with the movable part 9; by connecting and supporting the support parts at both ends of the pressure sensitive element 11 along the direction of the detection axis of the force to the movable part 9 and the second The process of connecting and supporting the pressure sensitive element 11 on the fixed part 35 of the housing 33; the process of joining the third housing 34 with the first housing 31 and the second housing 33; and the process of vacuum sealing the inside of the housing . The embodiments of the pressure sensor have been described above, however, the pressure sensitive element is not limited to the double tuning fork vibrator, and any piezoelectric vibrator can be used as long as the resonance frequency changes with tensile and compressive stresses. All can be used, for example, a SAW resonator, a thickness-shear vibration member, etc. can be used.

In addition, the surface of the diaphragm for detecting the pressure of the liquid to be measured may be coated so that the liquid or the like does not corrode the diaphragm. For example, a nickel compound may be applied to a metal diaphragm, and potassium may be applied to a piezoelectric crystal such as a crystal.

In addition, it is preferable that the first case and the second case are formed of metal such as stainless steel or aluminum because the processing is easy. In addition, when the third case is made of ceramics, the influence of heat on deformation of the pressure sensitive element can be alleviated.

The pressure sensor according to the invention of this application is based on a structure composed of a diaphragm, a pressure sensitive part and a housing as structural elements, and the pressure sensitive part shown in Figures 1 and 5 consists of a force transmission unit, a movable unit and pressure sensitive components.

In addition, the embodiment of the pressure sensor according to the present invention has been described for the case where the liquid is the pressure measurement object, but the present invention is not limited thereto, and can also be applied to the measurement of the pressure of gas or the like.

FIG. 6 shows a pressure sensor 40 according to the third embodiment, and FIGS. 7 and 8 show a perspective view of main components and a partially cutaway perspective view of the pressure sensor. The illustrated example is a modified example of the pressure sensor for detecting relative pressure shown in the first embodiment.

The pressure sensor 40 has a housing 42 made of a hollow cylinder. This casing 42 has a flange end plate 44 as an end plate constituting a first case (lower end plate), and a sealed terminal block 46 as a second case (upper end plate), and passes through a cylindrical side as a third case. The wall 48 surrounds the spaced-apart end plates to form a hollow airtight container. In the flange end plate 44 and the sealed terminal block 46, a first pressure input port 47 and a second pressure input port 49 are penetrated concentrically with the axis core of the housing 42. The first pressure input port 47, the second pressure input port The port 49 communicates with the internal space and opens to the outside. These openings are respectively separated from the inside by the first membrane 50 and the second membrane 52 , and the first membrane 50 and the second membrane 52 are integrated with the flange end plate 44 and the sealing terminal block 46 respectively. The first diaphragm 50 on the side of the flange end plate 44 is a member for receiving pressure, and the second diaphragm 52 on the side of the sealed terminal block 46 is a member for setting atmospheric pressure. Such a casing 42 is also formed in a state of being separated from the inside and outside, and the inside can be kept in a vacuum state by an air extraction unit (not shown), which is also the same as the first embodiment.

Inside the housing 42, a central shaft (force transmission unit) 54 is disposed along the axis of the housing 42, and the central shaft 54 connects the central areas of the inner surfaces of the first and second diaphragms 50, 52 to each other. rise, so that the first and second diaphragms 50, 52 are bonded together. And, in the middle of this central axis 54, a movable part 56 as a pressure sensitive element support is integrally provided, and one end of a pressure sensitive element 58 is mounted on the movable part 56, and the pressure sensitive element 58 is vibrated by a double tuning fork type. components, and the detection axis is set to be parallel to the axis perpendicular to the pressure bearing surfaces of the diaphragms 50 and 52 . The other end of the pressure sensitive element 58 is connected to a boss portion 60 serving as a pressure sensitive element support, and the boss portion 60 is provided on the sealing terminal block 46 of the housing 42 and protrudes inward. Thus, under the action of the pressure difference between the first diaphragm 50 for pressure receiving and the second diaphragm 52 for atmospheric pressure, if the central shaft 54 moves in the axial direction, the position of the movable part 56 changes accordingly. The sensitive element 58 generates an active force in the direction of the detection axis.

A plurality of support rods 62 a , 62 b serving as guide shafts are disposed inside the housing 42 , and the support rods 62 a , 62 b are parallel to the central axis 54 and located around the central axis 54 . These support rods keep the distance between the flange end plate 44 serving as the first case and the sealed terminal block 46 serving as the second case constant, so that the deformation of the case 42 due to the action of an external force or an arbitrary posture does not cause damage. This leads to a decrease in detection accuracy, which is the same as in the first embodiment.

In this third embodiment, in particular, the sealed terminal block 46 is used as the upper end plate, and the sealed terminal 64 penetrates through the terminal block 46 so that the signal of the pressure sensitive element 58 can be obtained from the outside.

According to such a third embodiment, the central shaft 54 is connected between the pair of diaphragms 50, 52, and the movable part 56 provided in the middle of the central shaft 54 moves in the axial direction integrally with the movement of the diaphragms 50, 52 (this is an action caused by the pressure difference received by the pair of diaphragms 50 and 52), and becomes an action corresponding to the force acting in the direction of the detection axis on the pressure sensitive element 58, which is a double tuning fork vibrator. Therefore, it is possible to configure a pressure sensor with high detection accuracy without using oil, and to have a compact and easy-to-assemble structure. In addition, the flanged end plate 44, the sealed terminal block 46 and the cylindrical side wall 48 form the housing 42 as a vacuum container, the flanged end plate 44 is integrally formed with the first diaphragm 50, and the sealed terminal block 46 is formed with the second diaphragm. The sheet 52 is integrally formed so that assembly can be performed easily. In order to attach the pressure sensor 40 to a container submerged (immersed) in the liquid to be measured, the flanged end plate 44 is joined to the liquid container to be measured via an O-ring and fastened with bolts. The O-shaped sealing ring surrounds the first diaphragm 50 . In this installation work, since the joint part of the diaphragm connected to the central shaft is not screwed in like the first embodiment, it is possible to prevent damage to the pressure sensitive element due to the extension of the central shaft. Bad condition of stretch force.

In addition, in this third embodiment, the central shaft 54 and the movable portion 56 as a support for fixing the pressure sensitive element may be integrally formed from one member by cutting. In this way, the movable part 56 will not shake or deviate relative to the fixed part of the shaft.

Next, the manufacturing process described in the third embodiment described above is shown in FIG. 9 . As shown in the figure, first, the sealed terminal block 46 is held using a jig A, and the second diaphragm 52 is joined to its pressure input port 49 by welding ( FIG. 9( 1 )). On the other hand, the flanged end plate 44 is held using a jig B, and the first diaphragm 50 is welded to its pressure input port 47 ( FIG. 9( 2 )). Next, the central shaft 54 is vertically bonded to the inner central portion of the second diaphragm 52 mounted on the sealed terminal block 46, however, the positioning jig 25 shown in FIG. 4 may also be used. Fit the positioning jig 25 on the boss portion 60 of the sealing terminal block 46 , insert the central shaft 54 with the adhesive attached to the front end into the positioning jig 25 for positioning, and erect and install it perpendicular to the central portion of the diaphragm 52 . In addition, the flange terminal board 44 is clamped and held by the jig B together with the jig C having insertion through holes through which the support rods 62 (62a, 62b) as guide shafts pass. In this state, the support rod 62 is inserted and attached with the front end embedded in the flange terminal plate 44 ( FIG. 9( 4 )).

Next, the flange terminal plate 44 is arranged opposite to the sealed terminal block 46, the front end of the guide shaft (support rod) 62 is embedded in the sealed terminal block 46 for bonding, and the other end of the central shaft 54 is bonded to the flange terminal block. The central portion of the first diaphragm 50 of the plate 44 is bonded. At this time, the positioning and installation of the two are realized by using jigs A, B, and C, and then only the jigs need to be divided and removed. The movable part 56 is attached to a part of the central shaft 54 with respect to the integrated flange terminal plate 44 and the sealed terminal block 46 . Since it is necessary to keep the height of the movable portion 56 from the flange terminal plate 44 at a predetermined height, the height adjustment jig D is used. The jig D is L-shaped as a whole, and the height adjustment of the seat part by entering into the gap between the upper end surface of the flange terminal plate 44 and the lower surface of the movable part 56 and maintaining the seat part relative to the sealed terminal block 46 The positioned position maintains the backplane section. The height can be adjusted by the thickness of the stand, and the space between the flange terminal plate 44 and the sealed terminal block 46 is kept constant by the back plate ( FIG. 9 ( 5 )).

Then, the pressure sensitive element 58 is installed between the boss part 60 of the sealed terminal block 46 and the movable part 56 of the central shaft 54 in such a way that the detection axis is parallel to the axis center of the central shaft 54, and after wiring processing, the mounting circle The side wall 48 of the cylinder seals the inside, and performs vacuum suction and partition (FIG. 9(6)). Finally, an IC (Integrated Circuit) is mounted on the outer end surface portion of the sealed terminal block 46, and wires are mounted, thereby completing the mounting (FIG. 9(7)).

In this way, it is possible to manufacture a pressure sensor that does not use oil, has high detection accuracy, and has a simple structure.

Next, a sectional view of the pressure sensor 70 according to the fourth embodiment is shown in FIG. 10 . The illustrated example is a modified example of the pressure sensor for detecting absolute pressure shown in the second embodiment. In particular, the central axis and the pressure sensitive element are arranged concentrically, and they are arranged on the side that passes through the pressure-receiving diaphragm. On the axis of the central area, this differs from the previous embodiment.

The pressure sensor 70 has a housing 72 made of a hollow cylinder. This case 72 has a flange end plate 74 as an end plate constituting a first case (lower end plate), and a sealed terminal block 76 as a second case (upper end plate), and passes through a cylindrical side as a third case. The wall 78 surrounds the spaced-apart end plates to form a hollow airtight container. A pressure input port 77 passes through the flange end plate 74 concentrically with the axis of the housing 72 . The pressure input port 77 communicates with the internal space and opens to the outside. The opening is separated from the inside by the first diaphragm 80 and integrated with the flange end plate 74 . The diaphragm 80 is used for receiving pressure of the liquid to be measured. The sealing terminal block 76 is configured as an end plate with both the pressure input port and the diaphragm omitted. Such a case 72 is also formed in a state where the inside and the outside are separated, and the inside can be kept in a vacuum state by an air extraction unit (not shown), as in the other embodiments.

Inside the housing 72 , a central shaft (force transmission unit) 84 is vertically erected in the central region of the inner surface of the diaphragm 80 , and the central shaft 84 is arranged along the axis of the housing 72 . Also, a movable portion 86 as a pressure-sensitive element support is integrally provided at the front end portion of the central shaft 84, and an end portion of a pressure-sensitive element 88 is mounted on the movable portion 86, and the pressure-sensitive element 88 is driven by the detection shaft It consists of a double tuning fork vibrator set coaxially with the central axis 84 . The other end of the pressure sensitive element 88 is connected to a support 90 which is provided in the central area of the sealed terminal block 76 of the housing 72 and protrudes inward. As a result, when the pressure-receiving diaphragm 80 is bent by the pressure of the liquid to be measured, the central axis 84 is moved in the axial direction, and the pressure-sensitive element 88 connected to the movable part 86 is detected along the pressure-sensitive element. Axial force.

In addition, a plurality of support rods 92 a , 92 b serving as guide shafts are disposed inside the housing 72 in parallel with the central axis 84 and located around it. These support rods keep the distance between the flanged end plate 74 as the first housing and the sealed terminal block 76 as the second housing constant, so that the deformation of the housing 42 caused by the external force or any posture will not cause any damage. The detection accuracy is lowered, which is the same as other embodiments.

In the fourth embodiment, as in the third embodiment, the sealed terminal block 76 is used as an upper end plate, and a not-shown sealed terminal penetrates the sealed terminal block 76 so that the signal of the pressure sensitive element 88 can be obtained from the outside.

According to such a fourth embodiment, the housing 72 as a vacuum container is formed by the flange end plate 74, the sealed terminal block 76, and the cylindrical side wall 78, and the flange end plate 74 is integrally formed with the diaphragm 80, so that the Assemble. The pressure-bearing diaphragm 80 is concentrically connected with the central shaft 84 on a straight line, so that the movable part 86 arranged at the front end of the central shaft 84 moves along the axial direction with the action of the diaphragm 80, thus acting as a double The pressure sensitive element 88 of the tuning fork type vibrator detects the force in the axial direction. Therefore, it is possible to configure a pressure sensor with high detection accuracy without using oil, and to have a compact and easy-to-assemble structure.

In addition, in this fourth embodiment, the central shaft 84 and the movable portion 86 serving as a support for fixing the pressure sensitive element may be integrally formed from one member by cutting. In this way, the movable part 86 will not shake or deviate relative to the fixed part of the shaft.

Claims (18)

1. A pressure sensor, characterized in that, The pressure sensor includes: shell; an installation part, which is connected to the shell and has a pressure input port; a diaphragm, which closes the pressure input port of the mounting part, and one side of the diaphragm is a pressure receiving surface; and The pressure-sensitive part takes the detection direction of the force as the detection axis, One end of the pressure-sensitive part is connected to the central area of the other side of the diaphragm, The other end of the pressure sensitive part is connected to the shell, The detection axis is substantially perpendicular to the pressure bearing surface. 2. The pressure sensor according to claim 1, characterized in that, The pressure sensitive part is composed of the following units: a force transmission unit, one end of which is in contact with the central region of the other side of the diaphragm; a movable unit fixed to the force transmission unit; and One end of the pressure sensitive element is connected with the movable unit, and the other end is connected with the shell. 3. The pressure sensor according to claim 1 or 2, characterized in that, The force transmission unit is a shaft. 4. The pressure sensor according to any one of claims 1 to 3, characterized in that, the pressure sensitive element has bases provided at both ends of the pressure sensitive element, A vibration part is provided between the base parts provided at the both ends. 5. The pressure sensor according to any one of claims 1 to 4, characterized in that, The material of the diaphragm is metal, ceramic or piezoelectric crystal. 6. The pressure sensor according to any one of claims 1 to 5, characterized in that, The shaft is made of stainless steel, aluminum or ceramics. 7. The pressure sensor according to any one of claims 1 to 6, characterized in that, The material of the shell is stainless steel, aluminum or ceramics. 8. A pressure sensor, characterized in that, The pressure sensor includes: a housing having a pressure input port; a diaphragm that closes the pressure input port of the housing, and the outer surface of the diaphragm is a pressure-bearing surface; and A pressure-sensitive part, inside the housing, one end of the pressure-sensitive part is connected to the central area of the inner surface of the diaphragm, the other end is connected to the housing, and the pressure-sensitive part is connected to the pressure-bearing surface of the diaphragm The vertical axis sets the detection axis. 9. The pressure sensor according to claim 8, characterized in that, The pressure-sensitive part is composed of a force transmission unit vertically connected to the diaphragm, and a pressure-sensitive element connected to the force transmission unit at one end and connected to the wall surface of the housing at the other end. 10. A pressure sensor, characterized in that, The pressure sensor includes: shell; a pressure input port coaxially disposed on opposite walls of the housing; a diaphragm, which closes the pressure input port, and the outer surface of the diaphragm is a pressure bearing surface; a force transmission unit connected inside the housing to the central area of the inner surface of the diaphragm; and One end of the pressure-sensitive element is connected with the force transmission unit, and the other end is connected with the housing, and the pressure-sensitive element sets a detection axis along an axis perpendicular to the pressure-bearing surface of the diaphragm. 11. A pressure sensor, characterized in that, The pressure sensor includes: shell; a pair of pressure inlets coaxially disposed on opposite walls of the housing; first and second diaphragms, which close the pressure input port, and the outer surfaces of the first and second diaphragms are pressure bearing surfaces; a force transmission unit, which is connected to the central area of the inner surface of the first and second diaphragms inside the housing; and One end of the pressure sensitive element is connected to the midway of the force transmission unit and the other end is connected to the housing, and the pressure sensitive element sets a detection axis parallel to an axis perpendicular to the pressure bearing surface of the diaphragm. 12. The pressure sensor according to any one of claims 8 to 11, characterized in that, A guide shaft parallel to the detection shaft is provided inside the housing. 13. The pressure sensor according to any one of claims 10 to 11, characterized in that, The force transmission unit is formed by a shaft, and the pressure sensitive element is arranged parallel to the shaft. 14. The pressure sensor of claim 10, wherein, The force transmission unit is formed by a shaft, and the pressure sensitive element is arranged coaxially with the shaft. 15. A pressure sensor, characterized in that, The pressure sensor includes: an outer shell, which is formed by mutually opposite end plate-shaped first and second shells and a third shell surrounding the first and second shells and forming side parts; first and second diaphragms, which respectively close the pressure input ports opening to the first and second housings; a central shaft, the central shaft is connected to the first and second diaphragms in the central area of the first and second diaphragms in the housing to form an integral body, so as to be able to transmit force; A pressure sensitive element, the two ends of which are installed on the movable support fixed on the central axis and the fixed support provided on the inner surface part of the housing, and the detection axis of the pressure sensitive element is set as parallel to said central axis; and A plurality of support rods are arranged around the central axis and connect the first and second housings. 16. A pressure sensor, characterized in that, The pressure sensor includes: an outer shell, which is formed by mutually opposite end plate-shaped first and second shells and a third shell surrounding the first and second shells and forming side parts; a first diaphragm, which closes the pressure input port opening to the first housing; a central shaft, in the housing, the central shaft is connected to the first diaphragm at the central area of the first diaphragm to form an integral body, so as to be able to transmit force; a pressure sensitive element, the two ends of which are installed on the movable support fixed on the end of the central shaft and the fixed support provided on the inner surface of the second housing, and the pressure sensitive element a detection axis is set coaxially with the central axis; and A plurality of support rods are arranged around the central axis and connect the first and second casings. 17. The pressure sensor according to claim 15 or 16, characterized in that, The central shaft and the movable support are integrally formed by cutting one part. 18. The pressure sensor according to any one of claims 15 to 17, characterized in that, The connecting portion of the central axis and the connecting portion of the diaphragm are joined together by an adhesive.

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